PurposeAn estimated 5.9 million people in South Africa are infected with HIV. Because antiretroviral therapy has made infection with HIV a treatable, chronic condition, HIV-infected individuals are now surviving to middle and older age. We investigated the implications of HIV status for breast cancer in South Africa.MethodsWe compared clinical and demographic characteristics of women newly diagnosed with a first primary breast cancer at Tygerberg Hospital, Cape Town, South Africa, from January 2010 to December 2011 by HIV status. We then compared HIV-positive patients with HIV-negative controls, matched 2:1 on age and ethnicity, with respect to chemotherapy regimens, toxicities, completion of systemic chemotherapy, and changes in CD4 cell count.ResultsOf 586 women with breast cancer, 31 (5.3%) were HIV positive, 420 (71.7%) were HIV negative, and 135 (23%) were untested for HIV. Women with HIV were younger than other women (P < .001). The groups did not differ in regard to stage at presentation, histologic subtype, tumor grade, nodal involvement, or hormone receptor positivity. More than 84% of patients who initiated systemic chemotherapy, regardless of HIV status, completed it without serious toxicity. Among HIV-positive patients receiving chemotherapy, the mean baseline CD4 cell count was 477 cells/µL (standard deviation, 160 cells/µL), and the mean nadir was 333 cells/µL (standard deviation, 166 cells/µL).ConclusionHIV-infected women were younger at breast cancer diagnosis than HIV-negative women but otherwise similar in phenotype and completion of chemotherapy. Longer term follow-up is needed to evaluate the effects of HIV, antiretroviral therapy, and chemotherapy on the survival and quality of life of patients with breast cancer.